Pengaruh jenis sambungan balok laminasi galar bambu wulung terhadap keruntuhan lentur

SUMIATI, Ir. H. Morisco, PhD

2005 | Tesis | S2 Teknik Sipil

Balok laminasi memiliki flesibilitas dimensi dan geometri serta efisiensi dalam penggunaan bahan, tapi untuk bentang yang panjang diperlukan adanya penyambungan. Bambu mempunyai kuat tarik dan kuat lentur yang tinggi jika dibandingkan dengan kayu, tapi mempunyai kelemahan dalam perangkaiannya. Agar bambu dapat dimanfaatkan secara optimal maka perlu diteliti pengaruh jenis sambungan yang efektif terhadap kuat lentur dan aplikasinya terhadap balok laminasi. Sebagai data pendukung dilakukan pengujian sifat fisika dan mekanika berdasarkan standar (Ghavami, 1990). Pengujian kuat lentur berdasarkan empat titik pembebanan (ASTM D 198–84). Ukuran balok ( 50 x 100 x 2400 mm) terdiri dari 20 lamina dengan ketebalan 5 mm. Jenis sambungan yang diterapkan adalah sambungan jari dan sambungan miring yang dipotong arah vertikal dan horisontal, sehingga didapatkan empat variasi sambungan yang diletakkan di tengah bentang pada daerah momen maksimum. Masing-masing jenis sambungan dibuat tiga balok, sebagai pembanding digunakan balok laminasi utuh. Hasil penelitian bambu wulung pada kadar air 15% didapatkan kerapatan = 0,594 gram/cm3, kuat lentur (MOR) = 91,467 MPa, kekakuan (MOE) = 13.421,66 MPa. Proses laminasi memberikan efek peningkatan kekakuan = 20,24%, sebaliknya penerapan sambungan justru menimbulkan penurunan kekakuan balok laminasi pada sambungan (jari vertikal= 3,1%; jari horisontal = 11,87%; miring vertikal = 31,59%; miring horisontal = 41,94%). Proses laminasi menyebabkan penurunan kuat lentur sebesar 33,53%, penerapan sambungan menyebabkan penurunan kuat lentur pada sambungan (jari vertikal = 37,76%; jari horisontal = 43,45%; miring vertikal = 71,36%; miring horisontal = 77,30%). Sambungan jari vertikal lebih efektif karena mempunyai kekuatan tertinggi sebesar 61,77%, jari horisontal, miring vertikal dan miring horisontal berurutan sebesar: 52,47%; 24,14%; 19,26%.

Glued-laminated beam has dimensional and geometrical flexibility and material usage efficiency. In order to get a long span, joint is needed. Bamboo has higher tensile strength and better bending strength than wood, but it has a weakness in its arrangement. It needs research on the influence of effective joint to the bending strength and its application to glued- laminated beam in order to optimize the use of bamboo. The test of physical and mechanical variety based on (Ghavami, 1990) a standard test method was conducted as the secondary data. The test of bending strength was conducted based on four points bending (ASTMD 198-84). The beam size of 50x100x2400 mms consisted of 20 layers of 5 mm thick. The joints applied were finger joints and scarf joints arranged in vertical and horizontal directions. Therefore, there were 4 varieties of joints placed in the center of beam span in the maximum moment area. There were 3 beams for each variety of joint; for comparison, an intact beam was needed. The research result of wulung bamboo at a moisture content of 15% gives a density of 0.594 gram/cm³, a modulus of rupture (MOR) of 91.467 MPa, a modulus of elasticity (MOE) of 13,421.66 MPa. The glued-laminated process gives an effect on the increase of modulus of elasticity (MOE), ie 20.24%, in contrast, the application of joint causes a decrease of modulus of elasticity (MOE) on glue laminated beam joint as follows: vertical finger joint of 3.1%, horizontal finger joint of 11.87%, vertical scarf joint of 31.59%, and horizontal scarf joint of 41.94%. The glued-laminated process also affects modulus of rupture (MOR) decrease equal to 33.53%, meanwhile the application of joint causes modulus of rupture (MOR) decrease of glued- laminated beam as follows: vertical finger joint of 37.76%, horizontal finger joint of 43.45%, vertical scarf joint of 71.36%, and horizontal finger joint of 77.3%. Vertical finger joint is more effective since it has the highest strength of 61.77%, followed by horizontal finger joint of 52.47%, vertical scarf joint of 24.14% and horizontal scarf joint of 19.26%.

Kata Kunci : Balok Laminasi Galar,Jenis Sambungan,Keruntuhan Lentur, glued-laminated beam, bending failure, end-joint